[DRILL-2264] Incorrect data when we use aggregate functions with flatten

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Later
• Fix Version/s: 1.0.0
• Component/s: Execution - Relational Operators
• Assignee: Jason Altekruse
• Reporter: Rahul Kumar Challapalli
• Created: 18/Feb/15 18:51
• Updated: 05/May/15 00:47
• Resolved: 05/May/15 00:47

Description

git.commit.id.abbrev=6676f2d

Data Set :

{
  "uid":1,
  "lst_lst" : [[1,2],[3,4]]
}
{
  "uid":2,
  "lst_lst" : [[1,2],[3,4]]
}

The below query returns incorrect results :

select uid,MAX( flatten(lst_lst[1]) + flatten(lst_lst[0])) from `temp.json` group by uid, flatten(lst_lst[1]), flatten(lst_lst[0]);
+------------+------------+
|    uid     |   EXPR$1   |
+------------+------------+
| 1          | 6          |
| 1          | 6          |
| 1          | 6          |
| 1          | 6          |
| 2          | 6          |
| 2          | 6          |
| 2          | 6          |
| 2          | 6          |
+------------+------------+

However if we use a sub query, drill returns the right data

select uid, MAX(l1+l2) from (select uid,flatten(lst_lst[1]) l1, flatten(lst_lst[0]) l2 from `temp.json`) sub group by uid, l1, l2;
+------------+------------+
|    uid     |   EXPR$1   |
+------------+------------+
| 1          | 4          |
| 1          | 5          |
| 1          | 5          |
| 1          | 6          |
| 2          | 4          |
| 2          | 5          |
| 2          | 5          |
| 2          | 6          |
+------------+------------+

Also using a single flatten yields proper results

select uid,MAX(flatten(lst_lst[0])) from `temp.json` group by uid, flatten(lst_lst[0]);
+------------+------------+
|    uid     |   EXPR$1   |
+------------+------------+
| 1          | 1          |
| 1          | 2          |
| 2          | 1          |
| 2          | 2          |
+------------+------------+

Marked it as critical since we return in-correct data. Let me know if you have any other questions

Issue Links

• is related to: DRILL-2232 Flatten functionality not well defined when we use flatten in an order by without projecting it
• relates to: DRILL-2181 Throw proper error message when flatten is used within an 'order by' or 'group by'